There are many types of frequency division multiplexed network technologies, including global systems mobile (GSM), time division multiple access (TDMA), and advanced mobile phone service (AMPS) and common frequency technologies like code division multiple access (CDMA). Likewise, there are many types of packet data technology that are being implemented with these mobile network technologies. For example, global packet radio services (GPRS) and enhanced data rate for GSM evolution (EDGE) technologies are being developed to implement packet data technology for personal communications services (PCS) such as GSM and TDMA networks, respectively.
These technologies are discussed by various standards, such as the Internet Engineering Task Force (IETF), the International Telecommunications Union (ITU) for International Mobile Telecommunications 2000 (IMT-2000) and the Telecommunications Industry Association (TIA) Standards. These standards define, among other things, specific layering techniques for categorizing specific functions for the transfer of frames, or groups, of data in a physical medium (e.g., air or wire). The standards also define specific parameters for the frame structure.
Many parameters related to the framing of data in a wireless network have a strong impact on the performance of the network. For voice application, a frame error correction code (FEC) and a frame length are chosen to provide sufficient performance, and acceptable voice quality, with respect to a signal to noise ratio (SNR), delay, and a frame error rate (FER). For data applications, the requirements for acceptable performance with respect to FER, SNR, and delay will differ for those of voice applications. The FEC employed for data applications may differ from that employed in voice applications, and the relationship between FER and SNR will differ as well. Furthermore, the FER, SNR, and delay requirements will differ between circuit and packet data applications. Further still, radio environment (e.g., multipath fading) will also have an impact on the FER performance and its relationship with SNR and frame length. Therefore, for these technologies, it is desirable to parameterize the data frames in order to achieve efficient operation depending on the radio environment, application, and deployment situation.
Consider for example a wireless network using CDMA2000 technology. CDMA2000 refers to a third generation wireless technology, or 3rd generation wireless cellular/PCS technology, based on interim standard IS-95 CDMA. CDMA2000 is similar to wideband CDMA, or “W-CDMA,” which refers to a 3rd generation wireless cellular/PCS technology based on spread spectrum CDMA proposed in Europe. Only CDMA2000 will be discussed for the sake of simplify and clarity, it being understood that different network technologies, including W-CDMA, will behave similarly.
Two types of coding that may be used with CDMA2000 are Turbo and Convolutional codes. For Turbo codes, the trend is for a decreasing SNR, given a fixed bit error rate (BER) or FER, as the frame length increases. For Convolutional codes, the BER remains relatively constant with frame length, for a constant SNR. Also, the FER degrades as the frame length increases. These two coding types will require different frame configurations for optimal performance.
Another factor in choosing a frame configuration is the complexity of the mobile unit. The specific choice of frame configuration will have both complexity and performance implications.
In furtherance of the CDMA2000 example, a typical frame may be 20 milliseconds (ms). As transmission rates increase, the number of bits in a 20 ms frame becomes very large. Several problems often result. For one, many wireless communication systems are tailored for voice instead of data. Decoding delays are less desirable in voice transmissions; bit errors are less desirable in data transmissions.
Considering these and other inherent problems, it is desired to have a telecommunications system that provides sufficient parameterization of the frame configurations in order to maximize the efficient operation of the cellular/PCS network.
It is also desired to have a telecommunications system that is flexible for balancing decoding delays vs. frame errors in an efficient manner.
It is further desired to maintain acceptable bit error rates and frame error rates.
It is still further desired to have a system that accommodates different transmission rates.